The present invention relates to refrigeration systems for transport cargo space and especially to shipping container refrigeration systems and more particularly to control systems employing microprocessors so as to enhance the performance and managed operation of such refrigeration systems.
When a product that requires refrigeration is shipped, the shipper, the receiver, and the carrier all need to have assurances that the product will accurately and reliably be kept at the temperature required for the product during its transit time. Transport refrigeration systems and controls have been developed through the years for trucks, railroad cars and modular shipping containers to provide generally improving temperature control reliability and accuracy, better manufacturing and operating economy, greater operating flexibility and other performance objectives.
One example of a prior art system which provided progress in the art through improved mode and sequencing control is that which is set forth in U.S. Pat. No. 4,419,866 filed by Leland L. Howland on June 9, 1982 and assigned to the present assignee. This system employs analog circuitry including relays for implementing the control concepts involved. Numerous other prior art examples could be cited to illustrate incremental development in the transport refrigeration control art to the point where it is today.
In any case, a need continues to exist for further improvement in reliability and accuracy of transport space temperature control, and especially for the facility with which temperature control reliability and accuracy can be managed. This is especially true in the case of transportable container refrigeration systems, which, unlike refrigerated trucks, have no individually assigned attendant who can by observation become alerted to any unusual conditions or events which would effect control performance or operating reliability.
Limited efforts have been made in the past to obtain benefits from applying microcomputer technology to the transport refrigeration art. For example, a computer based monitoring system is set forth in U.S. Pat. No. 4,234,926 entitled "System and Method for Monitoring and Diagnosing Faults in Environmentally Controlled Containers, Such System and Method Being Especially Adapted for Remote Computer Controlled Monitoring of Numerous Transportable Containers Over Existing On-Site Power Wiring" and filed on Dec. 5, 1978 by C. G. Wallace et al. and assigned to Sealand Service Inc. of Edison, NJ. That system provides extended information availability for operating management through fault diagnosis and remote computer data linking and other monitoring features.
To obtain still better manageability and better product reliability and performance, it is desirable that an application of microcomputer technology by made to transport refrigeration systems with greater depth and scope so that more flexible, accurate, and reliable space temperature control and data monitoring can be achieved than has heretofore been the case.